After one crime, then a second, then a third perpetrated most likely by one or more serial killers, Sepp must team up with Helene, a profiler. But quickly, the duo is kidnapped by an organization: a serial killers’ society organizes a Konvention (with a “k” for “killer”) in a grand hotel. On the program: workshops to learn how to cover their tracks, the latest FBI tracking methods, training with the most modern detection and jamming tools, testimonies, and more… But the Konvention rules are strict and forbid killers to give in to their impulses throughout the state and for the period of the Konvention. However, a serial killer kills congress participants, one after the other, imitating their practices. Sepp and Helene are instructed by the organizers, under threat of seeing their relatives tortured and killed, to pretend to be two congressmen, in order to expose the killer. But working for killers has consequences and they witness the murder of the real people they pretend to be. The killings follow one another and their employer gives them little time to investigate before any evidence is removed and their access to information is restricted. Will Sepp and Helene manage to arrest the killer? Will they be able to do so without any collateral damage?